Bearing Capacity and Shallow Foundations - Elements of Soil Mechanics - page 277

Self weight of soil:

W = × − ( B L B × L )× − ( z t )× γ soil col col soil

= ( 2 0 2 0 0 4 0 4 . × . − . × . ) × ( . 1 5 0. − 5 ) × 20

= 76 8 . kN

i/ short-term state

1. Combination 1 (partial factor sets A1 + M1 + R1)
From Table 5.1: γ G, unfav = 1.35; γ G, fav = 1.0; γ Q = 1.5; γ cu = 1.0; γ γ = 1.0; γ Rv = 1.0.
(iii) Design actions:
Design value of self weight of concrete and soil (unfavourable, permanent action):

W = ( W + W )× γ ,

d concrete soil G unfav

= ( 54 0 . + 76 8 . ) × 1 35 . = 176 6 . kN

Design value of the vertical structural (unfavourable) actions:

V = × V γ + × V γ = ( 800 1 35 × . ) + ( 350 1 5 × . ) = 1605 kN d G Q

G unfav , Q unfav ,

Design effect of actions (i.e. sum of vertical forces):

F W V = + = 176 6 1605 . + = 1781 6 . kN d d d

Overburden pressure: q = γ soil z = 20 × 1.5 = 30 kPa
(iii) Design material properties:

=

c 200

1

=

u k
cu

;

Design cohesion c : = 200 kPa u d ;

γ

=

γ
γ γ

20
1

=

k

Design weight density of soil : γ = 20 N m k /

3

d

(iv) Design geometry:

⇒ ′ = × = No eccentric loading , A B L 2 0 2 0 . × . = 4 0 . m

2

No inclined loading, ⇒ i c = 1.0
Foundation base horizontal, ⇒ b c = 1.0
s c = 1.2 (EN 1997-1: 2004, Annex D)
(v) Bearing resistance:

′ = +

R A / ( π 2 ) c b s i + q

u c c c

R

k =

4 0 . × [( 5 14 200 1 0 1 2 1 0 . × × × × . . . ) + 30 ] = 5054 4 . kN

R 5054 4

1 0

.

k

R = = = 5054 4 . kN d

γ .

Rv

From the results it is seen that the GEO limit state requirement is satisfied since the
design bearing resistance (5054.4 kN) is greater than the design effects of actions
(1781.6 KN).

R
F

5054 4
1781 6

.
.

d

Over-design factor , Γ = = = 2 84 .

d

2. Combination 2 (partial factor sets A2 + M2 + R1)
From Table 5.1: γ G, unfav = 1.0; γ G, fav = 1.0; γ Q = 1.3; γ cu = 1.4; γ γ = 1.0; γ Rv = 1.0.